Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
  • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
  • A61B3/12—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for looking at the eye fundus, e.g. ophthalmoscopes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
  • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
  • A61B3/102—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for optical coherence tomography [OCT]
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
  • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
  • A61B3/1025—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for confocal scanning
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
  • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
  • A61B3/14—Arrangements specially adapted for eye photography
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
  • A61B5/0062—Arrangements for scanning
  • A61B5/0066—Optical coherence imaging
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
  • A61B5/0073—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence by tomography, i.e. reconstruction of 3D images from 2D projections
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/02015—Interferometers characterised by the beam path configuration
  • G01B9/02027—Two or more interferometric channels or interferometers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/02015—Interferometers characterised by the beam path configuration
  • G01B9/02027—Two or more interferometric channels or interferometers
  • G01B9/02028—Two or more reference or object arms in one interferometer
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/02041—Interferometers characterised by particular imaging or detection techniques
  • G01B9/02048—Rough and fine measurement
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/0209—Low-coherence interferometers
  • G01B9/02091—Tomographic interferometers, e.g. based on optical coherence
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N21/4795—Scattering, i.e. diffuse reflection spatially resolved investigating of object in scattering medium
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
  • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
  • A61B3/1005—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for measuring distances inside the eye, e.g. thickness of the cornea
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
  • G01B2290/65—Spatial scanning object beam

Definitions

• the present invention relates to an imaging apparatus and an imaging method for imaging an object by using an optical coherence tomography, and more particularly to a radiation method of a measuring beam.
• an imaging apparatus for imaging an object by the use of an optical coherence tomography (OCT) using interference by a low coherence light
• OCT apparatus uses a character of light
• the OCT apparatus can acquire a tomographic image at the high resolution of about a micrometer, which is the order of a wavelength of light.
• OCT apparatus uses a character of light
• the examinee sometimes moves, blinks, or randomly joggles (flicks) during measurement.
• An OCT apparatus radiating a plurality of lights to an eye to be inspected can image the eye to be inspected at higher speed than that of an OCT apparatus radiating a single light to the eye to be inspected. At this time, it is desirable to configure the OCT apparatus radiating the plurality of lights to the eye to be inspected in such a way that either the speed of imaging or the quality of imaging can have priority to the other according to an imaging region of the object, such as the eye to be inspected.
• An imaging apparatus comprises: radiating unit for radiating a plurality of measuring beams to an object; changing unit for changing a positional relation among irradiation positions of the plurality of measuring beams radiated at a predetermined same layer of the object by the radiating unit; scanning unit for scanning the plurality of measuring beams in the positional relation changed by the changing unit; and acquiring unit for acquiring an optical coherence tomographic image of the object based on the plurality of measuring beams used for the scanning by the scanning unit.
• the imaging apparatus comprises: radiating unit for radiating a plurality of measuring beams to an object; changing unit for changing a positional relation among irradiation positions of the plurality of measuring beams radiated to the object by the radiating unit; scanning unit for scanning the plurality of measuring beams in the positional relation changed by the changing unit; acquiring unit for acquiring an optical coherence tomographic image of the object based on the plurality of measuring beams used by the scanning by the scanning unit; analyzing unit for analyzing a wide area image of the object acquired in a scanning region wider than that of acquiring the optical coherence tomographic image; and controlling unit for controlling the changing unit by using an analysis result of the analyzing unit.
• an imaging apparatus comprises: radiating unit for radiating a plurality of measuring beams to an object; scanning unit for aligning irradiation positions of the plurality of measuring beams, radiated onto a predetermined same layer of the object by the radiating unit, almost in a main scanning direction to scan the plurality of measuring beams; changing unit for changing scanning speeds of the plurality of measuring beams in the main scanning direction; and acquiring unit for acquiring an optical coherence tomographic image of the object based on the plurality of measuring beams used for the scanning by the scanning unit .
• an imaging method comprises the steps of: radiating a plurality of measuring beams to an object; scanning the plurality of measuring beams; acquiring an optical coherence tomographic image of the object based on the plurality of measuring beams; analyzing a wide area image of the object in a scanning region wider than that of acquiring the optical coherence tomographic image; and changing a positional relation among irradiation positions of the plurality * of measuring beams radiated to the object by using an analysis result of the step of analyzing .
• An OCT apparatus can change the positional relation among the irradiation positions of a plurality of measuring beams radiated to the object, such as an eye to be inspected.
• the OCT apparatus can be configured to give high priority to either the high-speed performance or the high image quality performance of imaging especially according to the imaging region of an object.
• FIGS. IA, IB, and 1C are diagrams for describing the configuration of an imaging apparatus in a first embodiment of the present invention.
• FIGS. 2A, 2B, 2C, and 2D are views for describing arrangements of measuring beams in the first embodiment of the present invention.
• FIGS. 3A, 3B, 3C, and 3D are views for describing acquiring regions of a tomographic image in the first embodiment of the present invention.
• FIGS. 4A and 4B are diagrams for describing the acquisition of a tomographic image of a horizontal arrangement in the first embodiment of the present invention.
• FIGS. 5A and 5B are flow charts for describing the operation of the imaging apparatus in the first embodiment of the present invention.
• FIGS. 6A, 6B, 6C, 6D, and 6E are diagrams for describing the configuration of the imaging apparatus in the first embodiment of the present invention.
• FIGS. 7A, 7B, 7C, and 7D are diagrams for describing the configuration of the imaging apparatus in a second embodiment of the present invention.
• FIGS. 8A, 8B, 8C, and 8D are diagrams for describing the configuration of the imaging apparatus of each embodiment of the present invention.
• FIGS. 9A and 9B are flow charts for describing the operation of the imaging apparatus of each embodiment of the present invention.
• FIGS. 1OA, 1OB, IOC, 1OD, 1OE, and 1OF are views for describing the arrangements of the measuring beams in a sixth embodiment of the present invention.
• an imaging apparatus (or also referred to as an imaging apparatus for imaging an optical coherence tomographic image of an object by radiating a plurality of measuring beams to the object) according to the present invention has the feature of changing the positional relation among irradiation positions of the plurality of measuring beams radiated to the object, such as an eye to be inspected (particularly to a predetermined same layer, such as a fundus surface of the eye to be inspected) . It is hereby possible to configure the imaging apparatus to be able to give priority to either the high-speed performance of imaging or the high image quality thereof according to an imaging region of the eye to be inspected.
• the imaging apparatus (OCT apparatus 100) includes changing unit (changing unit 4) for changing the positional relation, scanning unit (scanning unit 7) for performing scanning with a plurality of measuring beams in the changed positional relation, and acquiring unit (acquiring unit 1) for acquiring an optical coherence tomographic image of an object based on the plurality of measuring beams here.
• the changing unit is preferably means for changing intervals between a plurality of irradiation positions. This means that the densities of the plurality of irradiation positions can simply be changed. It is, hereby, possible to increase or decrease the number of times (number of times of irradiation) per unit time of irradiation to the scanning region by the scanning unit (scanning unit 7).
• the positional relation so as to increase the number of times for example, by arranging the irradiation positions almost in the main scanning direction of the scanning unit (scanning unit 7)) to the watching region (such as a macula or an optic disc) useful for diagnosis, a tomographic image having a high image quality in the watching region can be imaged.
• the number of times may be increased to an imaging region having a bad S/N ratio as a result of the analysis of the acquired tomographic image with the analyzing unit.
• the changing unit (changing unit 4) preferably change the width of the scanning unit (scanning unit 7) in the sub scanning direction in the plurality of irradiation positions.
• This can be realized by, for example, changing the arrangement of the plurality of irradiation positions from the main scanning direction of the scanning unit (scanning unit 7) to the sub scanning direction thereof or from the sub scanning direction to the main scanning direction with the changing unit (changing unit 4) .
• the plurality of measuring beams is radiated to the eye to be inspected, the averaging of the respective tomographic images imaged at the same place would enable the acquisition of a tomographic image having a high image quality.
• An imaging apparatus of the present embodiment is configured to measure an object, particularly a fundus (retina) .
• a watching region is determined on the basis of a result of the acquisition of a first tomographic image.
• the positional relation (the arrangement of a plurality of irradiation positions) of the plurality of irradiation positions acquired by radiating a plurality of measuring beams to the fundus could be changed.
• IB a schematic view for describing the configuration of the OCT apparatus.
• a tomographic image is acquired by scanning a retina part RT of an eyeball EB with a plurality of measuring beams there.
• An acquiring unit 1 of the present embodiment produces a tomographic image by performing the Fourier transformation of a signal detected by separating an interference light into its spectral components.
• This is an SD-OCT (also referred to as a spectral domain system in OCT), one of a FD-OCT (Fourier domain system in OCT) .
• the OCT apparatus according to the present invention is, however, not restricted to this system, but it is also possible to apply an SS-OCT and a TD-OCT.
• the direction perpendicular to the paper surface of FIG. IB is set as an X-axis
• the depth direction of the eyeball EB, crossed with the X-axis at right angles is set as Z-axis
• the direction crossed with the X-axis at right angles in the same plane as that of the Z-axis is set as a Y-axis.
• main scanning the scanning in the X-axis direction with the measuring beams
• the scanning in the Y-axis direction with the measuring beams will be referred to as sub scanning.
• the imaging apparatus of the present embodiment is configured as an imaging apparatus by the OCT for imaging a tomographic image of an object by using combined lights, produced by making a reference beam interfere with the respective plurality of returning lights of the plurality of measuring beams radiated to an object.
• a light emitted from an SLD 101 which is a low coherence light source, is split into three light fluxes in a beam splitter 102, and enters a fiber coupler 103.
• the fiber coupler 103 separates the entered light fluxes into a measuring beam flux Bm and a reference beam flux Br, and outputs the measuring beam flux Bm to a scanning optical system 104 through optical fibers and the reference beam flux Br to a reference beam collimator 108.
• the scanning optical system 104 also referred to as the scanning unit 7) condenses the input measuring beam flux Bm to a galvanometer mirror 106, and performs the scanning with the measuring beams.
• FIGS. 2A to 2D illustrate the arrangement of the irradiation positions of measuring beams in the scanning optical system 104
• FIG. 2A illustrates the case of making three measuring beams pi, p2, and p3 constituting the measuring beam flux Bm enter almost perpendicular to the main scanning direction (sub scanning direction).
• FIG. 2C illustrates the case of making the three measuring beams pi, p2, and p3 enter almost horizontally.
• FIGS. 2B and 2D illustrate the arrangements of the respective measuring beams to the main scanning direction on the retina RT. In FIG. 2B, the measuring beams pi, p2, and p3 are arranged perpendicularly to the main scanning direction, and in FIG.
• the measuring beams pi, p2, and p3 are horizontally arranged.
• the changing unit 4 changes the arrangement of the plurality of irradiation positions of the scanning unit 7 from the main scanning direction to the sub scanning direction or from the sub scanning direction to the main scanning direction.
• the galvanometer mirror 106 can be driven into two axes, and a scanner controlling unit 105 performs the drive control of the mirror so as to scan the retina RT with the measuring beams into the main scanning direction and the sub scanning direction.
• the measuring beam flux Bm used for the scanning, arrives at the retina RT, which is the object to be measured, through an objective optical system 107, and is reflected to arrive at the fiber coupler 103 again through the objective optical system 107 and the scanning optical system 104 there.
• the reference beam flux Br output from the fiber coupler 103, is reflected by a reference mirror 109 through the optical fibers and the reference beam collimator 108, and again arrives at the fiber coupler 103.
• the reference beam flux Br interferes with the measuring beam flux Bm to produce an interference light there, and the produced interference light is input into a signal detecting unit 110.
• the signal detecting unit 110 detects each interference light to output the detected interference lights as three electrical interference signals to a signal processing unit 111.
• the signal processing unit 111 produces three signals (hereinafter referred to as scans A) from the respective interference signals corresponding to the reflectances of the retina RT along the Z-axis direction by the signal processing, such as Fourier transformation, and outputs the produced three signals.
• FIGS. 4A and 4B illustrate the three scans A ASl, AS2, and AS3 in the horizontal arrangement illustrated in FIG. 2C and 2D together with the retina RT.
• the imaging apparatus includes the changing unit 4, changing the positional relation (arrangement) of the plurality of irradiation positions on the retina RT.
• the imaging apparatus is, hereby, configured to perform the imaging having a high image quality by changing the incident arrangement of measuring beams in a region in which the imaging of high resolution is required. That is, as minutely described in the following, the imaging apparatus is configured so as to image a tomographic image by changing the arrangement of the measuring beams pi, p2, and p3 to the horizontal arrangement illustrated in FIG. 2D in a region in which imaging of high resolution is required, and so as to perform scanning with the measuring beams pi, p2, and p3 in the vertical arrangement illustrated in FIG. 2B in the other region.
• the imaging apparatus performs scanning with the measuring beams arranged in the vertical arrangement illustrated in FIG. 2A to acquire a tomographic image with the acquiring unit 1 in the step of SlOO, which is a first acquiring step of acquiring a first tomographic image.
• Wl and Dl in FIGS. 3A .and 3C are sample numbers of tomographic images in the X-axis direction and the Y-axis direction corresponding to a measuring region Rl in a fundus.
• the sample numbers are set by an operator of the imaging apparatus according to the present embodiment.
• the measuring region Rl is set in a wide range (also referred to as a wide area region) including an optic disc OP and a macula MF of the fundus.
• an image in the measuring region Rl is also referred to as a wide area image .
• the measuring beams are used for the scanning in the vertical arrangement, and scans A by the respective measuring beams are arranged Wl scans in the X-axis direction to be a tomographic image corresponding to an X, Z-plane.
• the tomographic image is supposed to be referred' to as a scan B, three scans B is led to be acquired by only one time of main scanning, and the tomographic image of the measuring region Rl (wide area region) can be acquired at about three times the speed in comparison with the case of using one measuring beam.
• the tomographic image acquired at the step of SlOO will be referred to as a wide area tomographic image.
• the acquiring unit 1 outputs the wide area tomographic image acquired as above to an analyzing unit 3 and a display unit 5, and the display unit 5 stores the wide area tomographic image in a not-illustrated memory.
• the wide area tomographic image is analyzed as follows to determine a measuring region.
• the analyzing unit 3 analyzes the wide area tomographic image, acquired as above, to further specify a region important for diagnosis, and outputs the position to a controlling unit 2. That is, the analyzing unit 3 analyzes the wide area tomographic image, acquired precedently as above, to determine an image range of a tomographic image important for diagnosis, which tomographic image is to be succeedingly acquired.
• a region R2 around a part between the optic disc OP and the macula MF is determined as a region necessary for diagnosis of glaucoma as illustrated in FIG. 3A. This is because there is the necessity of minutely observing the state of the retina layer at this part in the diagnosis of glaucoma.
• the analyzing unit 3 analyses the measuring region Rl of a wide area tomographic image to detect a COP and a CMF, corresponding to the centers of the optic disc portion OP and the macula MF, respectively, and determines the measuring region R2 having a boundary including COP and CMF with an interposed predetermined width around them.
• the detection method of the CMF and the COP will be described later.
• the analyzing unit 3 outputs the coordinates (x ⁇ , y ⁇ ) of the top left corner of the measuring region R2 and the numbers of pixels W2 and D2 in the X and Y-axis directions, respectively, to the controlling unit 2.
• the positional relation among a plurality of irradiation positions (the arrangement of the plurality of irradiation positions) acquired by radiating a plurality of measuring beams to an object as follows is changed.
• the signals pertaining to the position and the number of pixels of the measuring region R2 are input from the analyzing unit 3 to the controlling unit 2.
• a command (signal) to change the three irradiation positions from the vertical arrangement, illustrated in FIG, 2A, to the horizontal arrangement, illustrated in FIG. 2C, is output from the controlling unit 2 to the changing unit 4.
• the changing unit 4 turns the three optical fibers guiding the measuring beam flux Bm by 90 degrees so as to be in the horizontal arrangement.
• the changing unit 4 for example, an actuator, such as a motor and solenoid, can be used, and the turning of the optical fibers is performed by operating a not-illustrated driving mechanism.
• the plurality of measuring beams is radiated from the ends of the plurality of optical fibers to the object, and the changing unit 4 is configured so as to turn the ends of the plurality of optical fibers.
• the turning is that around the radiation directions of the plurality of measuring beams as the turning axes.
• the tomographic image is acquired as follows.
• the controlling unit 2 outputs the position and the number of pixels of the measuring region R2, input from the analyzing unit 3 beforehand, to the acquiring unit 1, and the acquiring unit 1 performs the measurement of the region.
• FIGS. 4A and 4B describe the acquisition of the scans A at the time of changing the measuring beams into the horizontal arrangement.
• the scans A obtained by the measuring beams pi, p2, and p3 are denoted by ASl, AS2, and AS3, respectively.
• the signal detecting unit 110 performs the detection of interference lights at the timings illustrated in FIG. 4B. That is, if it is supposed that the interval between each of the measuring beams is ⁇ x to be an equal interval and the measuring beams move into the main scanning direction at a uniform velocity in the present embodiment, the relation among the measuring beams becomes the one illustrated in FIG. 4B.
• the signal processing unit 111 processes the detected interference signals, and primarily stores the produced three scans A ASl, AS2, and AS3 in a not-illustrated memory. If the similar sampling is performed, three scan A groups illustrated in the following (formula 1) are acquired by one time main scanning.
• the signal processing unit 111 averages three scans A corresponding to the same position on the X-axis to calculate one scan A. That is, a scan A AS(x) at a position x in the X-axis direction is calculated by the following (Formula 2).
• AS(x) (AS3(x - 2) + AS2(x - 1) + ASl (x) ) /3 (Formula 2)
• the tomographic image produced in the step of S400 will be referred to as a watching tomographic image in the following description. Because three scans A are averaged as above, random noise is suppressed, and the S/N ratio or the resolution of the watching tomographic image is improved in comparison with the wide area tomographic image acquired in the step of SlOO, and the watching tomographic image becomes a tomographic image suitable for more minute observation. Furthermore, if the sampling interval of the interference signals is set to be shorter than that in the step of SlOO in the present step, it is also possible to acquire a tomographic image having higher resolution.
• a tomographic image is displayed as follows.
• the display unit 5 arranges two tomographic images input from the acquiring unit 1 to display them.
• FIG. 6E illustrates the form of the display.
• the display unit 5 is a liquid crystal monitor M, and the display unit 5 displays a wide area tomographic image Tl and a watching tomographic image T2 side-by-side. Thereby, it is possible to observe a minute tomographic image of a region more important for diagnosis while observing the state of a wide range retina.
• the scan B is selected as follows.
• the analyzing unit 3 selects one scan B from the input wide area tomographic image as an analysis object. For this, it is only necessary to select, for example, the tomographic images illustrated in FIG. 3B in ascending order of the Y-coordinates .
• the analyzing unit 3 detects an inner limiting membrane from the selected scan B.
• the inner limiting membrane is a layer contacting with the vitreous body in the retina layer, and is the part denoted by ILM in FIG. 6B.
• the analyzing unit 3 applies a low pass filter to the scan B, and, next, acquires the position of a pixel at which the difference between adjoining pixels is equal to or more than a threshold Tl and the Z-coordinate is the smallest in the Z-axis direction to each scan A constituting the scan B after the processing. That is, if the profile of the pixel values of the scan A AS in FIG. 6B is the one illustrated in FIG.
• the analyzing unit 3 detects z ⁇ , the minimum z-coordinate among those at which the differences between adjoining pixel values exceed Tl.
• An appropriate value for detecting the inner limiting membrane is selected from a plurality of tomographic images as the threshold Tl beforehand to be stored in a not-illustrated memory in the analyzing unit 3 here. This process is performed to all the scans A constituting the scan B. Because the number of pixels of the wide area tomographic images in the X-axis direction is Wl, Wl coordinate values PILM in the Z-axis direction, which are expressed by the following (Formula 3) are acguired to each scan B as a result.
• PILM ⁇ z ⁇ , zl, z2, ..., zwl - 1 ⁇ (Formula 3)
• the analyzing unit 3 detects whether the macula MF and the optic disc OP exist in the scan B that is the object now or not from the coordinate values PILM in the Z-axis direction. To put it concretely, as illustrated in FIG. 6D, the analyzing unit 3 detects two peaks (xf, zf) and (xp, zp) of the coordinate values PILM in the Z-axis direction corresponding to the macula MF and the optic disc OP, respectively. If the two peaks are not detected here, the process of the analyzing unit 3 moves to the step of S205. If the two peaks are detected, the process of the analyzing unit 3 moves to the step of S204.
• the inner limit position is stored as follows.
• the analyzing unit 3 stores the two peak coordinates (xf, zf) and (xp, zp) , detected at the step of S203, in the not-illustrated memory in the analyzing unit 3 together with the coordinate value in the Y-axis direction of the scan B in which the peak coordinates (Xf, zf) and (xp, zp) have been detected.
• the last scan B is performed as follows.
• the analyzing unit 3 judges whether the scan B which is now set as the object is the last scan B of the wide area tomographic images or not. If it is true, the process is moved to the step of S206. If it is not true, the process is moved to the step of S201.
• the central coordinates of the macula MF and the optic disc OP are determined as follows.
• the analyzing unit 3 detects the center position of the macula MF and the optic disc OP from the peak values stored in the step of S204.
• the coordinate value in the X-axis direction of the macula MF is set to xf_max
• the coordinate value in the Y-axis direction is set to the coordinate value in the Y-axis direction of the scan B in which the peak value has been detected. That is, if the coordinate value in the Y-axis direction of the scan B is set to yf, then the coordinates of the center CMF of the macula MF become (xf_max, yf) . Similar processing is performed to the optic disc OP, and the position of the center COP is acquired.
• the analyzing unit 3 determines the measuring region R2 as a range as the result of addition of a certain offset to the CMF and the COP.
• This offset value may be stored in the imaging apparatus as a device parameter of the imaging apparatus as a value necessary at the time of imaging a normal object (subject). Alternatively, the operator of the apparatus may input the offset value with a not-illustrated user interface before imaging.
• the imaging apparatus by the present embodiment can acquire a wide range tomographic image speedy by performing scanning with a plurality of measuring beams in the vertical arrangement. Then, by performing measurement of the watching region acquired by analyzing the tomographic image as an object by changing the measuring beams to the horizontal arrangement, by which a high S/N ratio or high resolution can be acquired, a tomographic image of a high image quality can be acquired while suppressing the increase of a measuring time.
• a tomographic image having a high image quality in a part of the region of an image range it is possible to image only the part relatively densely over time under the conditions set for enhancing the image quality thereof.
• the present invention is not limited to this, but an arbitrary number of measuring lights, which are two or more, can be used.
• the wide area tomographic image and the watching tomographic image are severally once imaged in the present embodiment, the present invention is not limited to this.
• the watching tomographic image may be imaged a plurality of times, and the scans A may be acquired more finely while gradually narrowing the measuring range.
• the present embodiment sets a fundus retina as an object and acquires a tomographic image especially effective for the diagnosis of glaucoma
• the present invention is not limited to this.
• the present invention can realize an imaging apparatus capable of enhancing the speed of measurement overall and acquiring a tomographic image having a higher image quality in an important part not only to the measurement by the OCT used in the diagnosis of the other diseases of the fundus retina as an object, it is needless to say, but also to the measurement by the OCT used in the other medical departments and the fields other than medical service.
• the imaging method according to the embodiment may be stored in a computer-readable storage medium (such as, a flexible disc, a hard disc, an optical disc, a magneto-optical disc, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, an EEPROM, and a Blu-ray Disc) as a program for enabling a computer to execute the imaging method.
• a computer-readable storage medium such as, a flexible disc, a hard disc, an optical disc, a magneto-optical disc, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, an EEPROM, and a Blu-ray Disc
• the present invention may be a program for enabling a computer to execute the imaging method.
• the first embodiment is configured to display a wide area tomographic image and a watching tomographic image side-by-side as illustrated in FIG.
• FIG. 7A illustrates the configuration of an imaging apparatus of the present embodiment.
• the configuration of FIG. 7A is the same as that of the first embodiment illustrated in FIG. IA other than an added image synthesizing unit 6, and accordingly the descriptions of the overlapping parts will be omitted.
• the present embodiment will be described mainly about the operation of the display unit 5 and the image synthesizing unit 6 at the step of S500 with reference to the flow chart illustrated in FIG. 7B.
• a tomographic image is acquired as follows.
• the image synthesizing unit 6 receives the inputs of both of a wide area tomographic image and a watching tomographic image from the acquiring unit 1. Furthermore, the image synthesizing unit 6 receives an input of the offset coordinate values (x ⁇ , y ⁇ ) of a watching tomographic image in the case of adopting the wide area tomographic image as a criterion from the acquiring unit 1.
• FIG. 7C illustrates the relation between the measuring region Rl of the wide area tomographic image expressed by the offset coordinate values and the measuring region R2 of the watching tomographic image.
• the offset coordinate values (x ⁇ , y ⁇ ) can be calculated by the acquiring unit 1 when the analyzing unit 3 ' determines the measuring region R2 in S200 of the flow chart illustrated in FIG.
• the image synthesizing unit 6 synthesizes the input wide area tomographic image and the watching tomographic image to one tomographic image.
• the synthesized tomographic image will be referred to as synthesized tomographic image in the subsequent description.
• the synthesis of the tomographic images is performed by substituting the pixels of the watching tomographic image for the pixels of the positions expressed by the offset coordinate values (x ⁇ , y ⁇ ) in the wide area tomographic image as illustrated in FIG. 1C, and the produced synthesized tomographic image is output to the display unit 5.
• the synthesized tomographic image is displayed as follows.
• the display unit 5 displays the input synthesized tomographic image on a monitor M.
• FIG. 7D is an example of a display mode at this time, and one scan B in the synthesized tomographic image is displayed.
• Tl' is a synthesized tomographic image, and a corresponding region is replaced with the data of the watching tomographic image T2 as illustrated by broken lines.
• the scan B image of the synthesized tomographic image Tl' is displayed as a two- dimensional image in the aforesaid display mode
• the ' present invention is not limited to this, but the synthesized tomographic image Tl' may three-dimensionally be displayed by volume rendering.
• boundary lines may be displayed by being superimposed on the tomographic image in order to be able to sight the boundaries of the watching tomographic image. For example, by displaying the boundary parts with the broken lines as illustrated in FIG. 7D, an observer can easily discern the part due to the watching tomographic image.
• the aforesaid embodiments are severally configured to change the scanning direction thereof from the vertical arrangement of the measuring beams to the horizontal arrangement of them at the time of acquiring two tomographic images, but the present invention is not limited to such a configuration.
• a third embodiment of setting the arrangement of the measuring beams thereof only to the horizontal arrangement, and of substantially changing the distances between the measuring beams will be described.
• the intervals between the measuring beams are changed as follows.
• the controlling unit 2 receives the inputs of the position and the number of pixels of the measuring region R2 from the analyzing unit 3, the controlling unit 2 outputs a command of changing the intervals between the three measuring beams to the changing unit 4.
• the changing unit 4 changes the arrangement so that the intervals between the three measuring beams on the fundus retina, which is the object to be measured, become relatively narrower in comparison with those at the step of SlOO in response to the command.
• the changing unit 4 changes the arrangement so that the lengths of the measuring beam intervals d, illustrated in FIG. 8A, become relatively smaller on the retina. This may be realized by mechanically changing the distances between the three optical fibers, but the present embodiment realizes it by controlling the speeds of the measuring beams in main scanning not by physically changing the intervals between the actual measuring beams.
• a watching tomographic image is acquired as follows.
• the changing unit 4 outputs a signal for changing the speed of the main scanning to the scanner controlling unit 105 in the acquiring unit 1.
• the scanning unit 7 is controlled so as to change the speed of the main scanning by the scanner controlling unit 105.
• the acquiring unit 1 acquires a watching tomographic image having a high image quality.
• FIG. 8B is a diagram illustrating the loci of the measuring beams in the scanning in the present embodiment. In FIG.
• broken lines express the loci of the respective measuring beams at the time of acquiring a wide area tomographic image in the step of SlOO, and on the other hand, solid lines express the loci of a watching tomographic image acquired in the step of S400.
• each measuring beam moves by 2 ⁇ x in one sampling period at the time of acquiring the wide area tomographic image
• each measurement ling moves by ⁇ x at the time of acquiring the watching tomographic image. Consequently, the intervals between the respective measuring beams substantially become double on the retina, and the sample number of the wide area tomographic image in the X-axis direction becomes a half, but the tomographic image can be acquired for a half time.
• the imaging apparatus by the present invention can be realized with a simple configuration without mechanically changing the arrangement of the measuring beams.
• the analyzing unit 3 is configured to determine the measuring region of the watching tomographic image by analyzing the wide area tomographic image, but the present invention is not limited to such a configuration.
• the method of determining a measuring region of the watching tomographic image on the basis of the imaging information pertaining to the past same object (subject) will be described.
• the configuration of the imaging apparatus by the present embodiment is the same as that of FIG. IA, but the configuration is different from that of FIG.
• the imaging information corresponds to a part regarded as the region to be watched in the past imaging. That is, as described above, in the case where the imaging apparatus is an ophthalmologic imaging apparatus, the past diagnostic information of the same patient is read as the imaging information by the analyzing unit 3.
• the diagnostic information is the information pertaining to a lesion area, which has been diagnosed in a past examination.
• the measuring region R2 of the watching tomographic image acquired in FIGS. 6A to 6E is saved as past diagnostic information, and the analyzing unit 3 can read the measuring region R2 through a diagnostic information acquiring unit 303 in FIG.
• FIG. 9A is a flow chart illustrating the operation of the imaging apparatus in the present embodiment.
• the same processing parts as those of the flow chart of each of the aforesaid embodiments are denoted by the same marks as those of the aforesaid embodiments, and the flow chart is different from those of the aforesaid embodiments in that the steps of S600 and S700 are added. Accordingly, the descriptions of the same parts are omitted, and the added parts will be described in the following.
• the analyzing unit 3 checks whether the diagnostic information pertaining to the same object (subject) exists or not after the completion of the acquisition of the wide area tomographic image in the step of SlOO. It is only necessary for performing this to retrieve the tomographic image having the ID number same as the one peculiar to each patient, which is an object (subject). It is supposed that the diagnostic information is saved in a not-illustrated storage apparatus of the imaging apparatus illustrated in FIG. IA, and that the ID number of the patient of the present measuring object is read into the analyzing unit 3 with a not-illustrated user interface before imaging. If the past diagnostic information exists here, the process moves to the step of S700.
• a measuring region is determined from the past diagnostic information as follows.
• the analyzing unit 3 determines the measuring region R2 stored as the past diagnostic information as a new measuring region as described above.
• the past diagnostic information is not limited to this, but the past diagnostic information may be the region saved as a lesion area in a past diagnosis .
• the imaging apparatus of each of the aforesaid embodiments is configured to determine the measuring region of a watching tomographic image from a wide area tomographic image or past diagnostic information, to change the arrangement of measuring beams, and to acquire a watching tomographic image
• the present invention is not limited to such a configuration.
• the analyzing unit of the present embodiment analyzes whether an abnormal structure of a subject is included in a tomographic image or not.
• the controlling unit according to the present embodiment is configured to be able to determine whether to acquire a tomographic image again or not according to the existence of the abnormal structure .
• FIG. 9B is a flow chart illustrating the operation of the imaging apparatus in the present embodiment.
• the parts performing the same operation as that of the aforesaid ones are omitted to be described, and the parts peculiar to the present embodiment will be described in the following.
• a wide area tomographic image is analyzed as follows.
• the analyzing unit 3 analyzes the wide area tomographic image to detect whether a structure different from normal ones is included or not. For example, if a leucoma L exists on a fundus as illustrated in FIG. 8C, the pixel values in the region of the leucoma L become larger than those in the other regions. This is because the reflectance in the leucoma L is higher than those in the other regions of the fundus.
• the analyzing unit 3 analyzes each of the scans A constituting the scan B to examine the existence of the parts in which the pixel values exceed those in the regions of normal structures greatly, and thereby the existence of the leucoma L can be judged.
• the leucoma is a swelling (soft leucoma) of a part of a nerve fiber on a retina or a clot of constituent parts of the blood (hard leucoma) in a blood vessel on the retina.
• the existence of a pixel exceeding a predetermined threshold TL is examined.
• the continuity of the pixels exceeding the predetermined threshold TL is examined.
• the number of continuous pixels is counted.
• the process advances to the step of S300. If it is judged that the abnormal structure does not exist, the process advances to the step of SlOOO.
• a tomographic image is displayed and saved as follows.
• the step of SlOOO is basically similar to the step of S500
• the step of S900 is different from the step of S500 in displaying only the wide area tomographic image if it is judged that there are no abnormal structures at the step of S900.
• the displayed tomographic image is saved in a not- illustrated storage apparatus, such as a storage medium of a hard disc, an MO, and the like, as a file.
• FIG. 8D illustrates the format of the saved file. This file includes the ID number capable of specifying a patient, the information such as the date and time of imaging, an analysis result in the step of S800, and tomographic image data.
• the changing unit 4 changes the arrangement of the measuring beams from the vertical arrangement to the horizontal arrangement by turning the optical fibers in the aforesaid first embodiment
• the present invention is not limited to such a configuration.
• the mode of acquiring a wide area tomographic image and a watching tomographic image without mechanically turning the optical fibers will be described.
• the present embodiment is different from the embodiment of FIG. 5A in the method of changing the arrangement of the measuring beams in the step of S300, the description will mainly be given to this part, and the minute descriptions of the other parts will be omitted.
• FIGS. 1OA to 1OF illustrate the arrangements of the measuring beams of the scanning optical system 104 in the present embodiment, and five optical fibers are provided in total. It is enabled to select three of the five optical fibers to radiate measuring beams. Accordingly, it is supposed that the beam splitter 102 illustrated in FIG. IB splits the outputs of the SLD 101 into five in the present embodiment. Furthermore, not-illustrated shutter mechanisms are provided between the beam splitter 102 and the fiber coupler 103, to enable the changing of the arrangement of the measuring beams entering an eye to be inspected.
• the imaging apparatus by the present invention forms measuring beam fluxes in the vertical arrangement by blocking out p4 and p5 with the shutters as illustrated in FIG. 1OA in the step of SlOO for acquiring a wide area tomographic image on the basis of such a configuration.
• the wide area tomographic image is analyzed to determine a measuring region of a watching tomographic image.
• the measuring beam fluxes of the horizontal arrangement can be formed as illustrated in the FIG. 1OC. Because the subsequent process is similar to that of the first embodiment, the description thereof is omitted.
• the measuring beam fluxes can be formed by selecting the measuring beams as illustrated in FIG. 1OE when a wide area tomographic image is acquired or as illustrated in FIG. 1OF when a watching tomographic image is acquired.
• similar effects can be acquired by changing the radiation pattern of a plurality of measuring beams without turning the optical fibers in the present invention.
• the number of the measuring beams to be radiated is not limited to those in FIGS. 1OA to 1OF in the present invention.
• the present invention is not limited to the aforesaid modes, but can be realized in various modes.
• the imaging apparatus illustrated in FIG. IA can be realized by hardware or a combination of hardware and software.
• each section in FIG. IA other than the acquiring unit 1 corresponds to a circuit or an ASIC for realizing a specific function in the case of hardware, or a module in the case of software.
• the software can be made to be a module operating on a general purpose PC.
• the storage apparatus of the tomographic images has been described to be in the imaging apparatus in the fifth embodiment, the storage apparatus can be configured as an image server connected to the imaging apparatus through a network.
• aspects of the present invention can also be realized by a computer of a system or apparatus (or devices such as a CPU or MPU) that reads out and executes a program recorded on a memory device to perform the functions of the above-described embodiment (s) , and by a method, the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory device to perform the functions of the above-described embodiment (s) .
• the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory device (e.g., computer-readable medium) .

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• 2010
  • 2010-03-24 JP JP2010068281A patent/JP5627260B2/ja not_active Expired - Fee Related
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